Olfactory Bulbectomy frequently results in increased aggressiveness and irritability. Crowded bulbectomized gerbils have previously been found to demonstrate such aggressiveness to a rather severe degree. The hormonal mechanisms underlying this aggressiveness will be investigated in the proposed experiment. Male gerbils will be either sham operated, or bulbectomized, and in addition will either be castrated, receive a pellet impregnated with dexamethasone, or will receive a plain silastic pellet. In addition, females will be bulbectomized and sham operated. After recovery from surgery, all animals will be assigned to groups of 10, all of the same experimental condition. Animals will be observed daily in their home cages for evidence of aggressiveness. In addition, animals will be given social interaction tests with other animals of their same hormonal condition, but opposite olfactory condition. Difference in bulbectomy-induced aggression will be attributed to differences in the hormonal state of the animal.